The author presents an analysis of how speakers establish references in conversation. Further, this paper focuses on what words of a reference are conventionalized as speakers coordinate multiple times. The author explores how the co-occurrence of the reference terms with the referent can be a good predictor of what words are conventionalized over time. In order to study this, the author created an online version of the reference game from Clark and Wilkes-Gibbs (1986) experiment, where a matcher and director must describe a set of ambiguous shapes to each other many times. By creating an online version of this reference game the author was able to gather significantly more data and analyze the data with computational tools. Results prove that co-occurrence is a useful predictor of terms which are conventionalized, providing a first step for accounting for statistical inference in the process of conventionalization.

Social behaviours have been widely studied in behavioural economics and psychology. However, the origins of these behaviours in the brain are poorly understood. In this dissertation I will discuss two main avenues of study which constituted separate projects during my PhD candidacy. The first section contains experiments in which I collaborated with Dr Raymundo Báez-Mendoza on the topic of inequity. The second part includes a study on coordination and cooperation behaviour in macaques. Inequity is a concept ubiquitous in daily life. It is the difference between one’s own reward and that of another. There have been several studies that have suggested inequity affects brain activity. However, few studies have touched upon how this parameter is incorporated in neuronal activity. In the experiments that will be described here, monkeys (Macaca mulatta) performed actions to obtain rewards for both themselves and another. The level of inequity in these rewards was manipulated by varying the magnitude of own and other’s rewards. We then proceeded to study neuronal activity by means of single neuron recordings in the striatum of two macaques. We found that inequity modulated task related activity in about 32% of recorded striatal neurons. In addition to this study on inequity we also recorded some sessions in which one of the animals made choices with varying rewards for self and other. From these results, I attempted to characterise behaviour with regards to own reward and inequity in choice situations. Inequity has been considered a contributing factor in explaining cooperation behaviour. Coordination and cooperation are important and frequently observed behaviours. To study coordination and cooperation, I designed an experiment in which the combination of two monkeys’ choices determined the rewards for both animals. In this dissertation I attempt to address how the animals perform combined choices (playing together vs. alone) as well as the nature of their behaviour (e.g. pro-social vs. self-interested). The aim of this work was to characterise what type of information the animals use to solve these tasks. This is vital if one is to study these concepts in the brain using macaques as a model. In summary, this work contributes to a better understanding of social behaviour and provides an example of how this social behaviour is computed in the brain.

A bank run occurs when a large number of customers withdraw their deposits from a financial institution at the same time. This can destabilise the bank to the point where it runs out of cash and thus faces sudden bankruptcy. As more people withdraw their deposits, the likelihood of bankruptcy increases, thus triggering further withdrawals. In game theory this type of situation can be modelled as a “coordination game”, that is, a game with two pure equilibria: If sufficiently many people keep their money in the bank, then it will not default and it is rational for everyone to keep their money in the bank. On the other hand, if sufficiently many people withdraw their deposits the bank will default and it is then rational for everyone to try to withdraw their deposits. The overall objective of this study is to explain the phenomenon of bank runs by introducing the Diamond–Dybvig model. This model assumes that the function of a bank is to offer both long-term loans for investments and relatively short-term deposit service. Bank runs comes out as one of two equilibria when too many withdraw early before the long-term loans is paid back. Our task is to find out the condition that can lead to bank runs and more importantly, we will suggest two ways to address the problem of bank runs.

京都大学 / 新制・課程博士 / 博士(経済学) / 甲第24382号 / 経博第669号 / 新制||経||303(附属図書館) / 京都大学大学院経済学研究科経済学専攻 / (主査)教授 関口 格, 准教授 陳 珈惠, 教授 渡辺 誠 / 学位規則第4条第1項該当 / Doctor of Economics / Kyoto University / DFAM